The invention relates to flexible pipes and tubular conduits, but more particularly, the invention relates to flexible buoyant hose which includes distinct plies of spirally extending material.
Special purpose hoses such as buoyant hose typically include a tube, cover and reinforcement. Additional structure is usually needed to give the hose desired buoyancy. For example, floats may be attached to a hose or as in some more preferred hose constructions, integral float chambers are included.
One type of integral float chamber includes one ply of one or more pieces of tubing helically spiralled around a tube at substantially the same diameter. The helically extending float chamber may be filled with cellular material such as disclosed in U.S. Pat. No. 3,119,415. The cellular material of such a hose substantially reduces the probability of flooding the float chamber.
Examples of buoyant hose with a single ply of spirally extending tubular chambers not filled with foam are disclosed in U.S. Pat. No. 3,117,596 and British Pat. No. 1,361,215. Such single ply constructions inherently introduce a possibility of reduced buoyancy capability over the expected life of the hose.
The float or tubing diameter must be quite large relative to the size of the tube to effect a chamber having sufficient buoying capability when a single ply of spiralled tubing is used. The numbers of tubes which can be used in a single ply to effect buoyancy are quite few. For example, one spiralled piece of tubing may be used which is disclosed in the U.S. Pat. No. 3,119,415 or up to twenty pieces of tubing may be used as disclosed in the U.S. Pat. No. 1,361,215. Hose buoyancy cannot be achieved by using more tubing in a single ply because the effective specific gravity of such tubing increases as the diameter thereof decreases.
Large diameter float tubing is more subject to collapse than smaller diameter tubing; it is also easier to flood than smaller diameter tubing. This contributes to possibility of losing hose buoyancy. As brought forth above, the problem of flooding large diameter tubing is substantially overcome by filling the tubes with foam.
However, as tubing diameters increase, tubing collapse resistance decreases. Collapse resistance may be enhanced by individually reinforcing the spiralled tubing as is disclosed in the U.S. Pat. Nos. 1,361,215 and 3,117,596.
Empty tubing contributes more to buoyancy than does a foamed filled tubing. However, foam is only necessary to lower the probability of flooding the single ply of large diameter tubing.
Foam disposed exteriorly of single ply tubing is susceptible to collapse because it must support the weight of a floating hose.